Broca's area & Wernicke's area

1. Broca's area & Wernicke's area • Speech is an important function controlled by two main regions of the brain, Broca's area and Wernicke's area. Broca's area is in the frontal lobe and is responsible for generating meaningful speech. People who sustain damage in Broca's area are often unable to say anything that makes sense, even though they are able to understand other people. Wernicke's area is necessary for speech recognition. Damage to Wernicke's area results in an inability to comprehend spoken language, a very disabling condition to be sure. Interestingly, the two speech centers are confined to only one side of the brain, typically the dominant left side. This is different than most brain functions which are handled by the analogous brain regions on both sides.

2. Functional Neuroimaging Functional neuroimaging uses techniques, such as functional magnetic resonance imaging (fMRI), to visualize brain function by visualizing changes in chemical composition of brain areas or changes in the flow of fluids that occur over timespans of seconds to minutes

3. Principle of Compositionally • How do humans manage to stuff an infinite language into their finite brains? • There is a systematic relation between the meaning of the whole and that of its parts

4. Sources of ambiguities • lexical • word sense: bank (river)/bank (finance) • part of speech: plan (noun)/plan (verb) • structural They are annoying children ((They) (are annoying) (children)) ((They) (are) (annoying children)) • Scopal • Every student knows two languages • Each student knows two languages. It is not necessary that all students know the same two languages • There are two languages that are known by all students

5. Ambiguity • Natural languages are ambiguous, two examples: • I withdrew some money from my bank. • (what bank? river bank? financial bank?) • Sarah called Janet. She … • (who does ‘she’ refer to? Sarah or Janet?)

6. Sources of ambiguities (2) • Pragmatic • Can you pass the salt? • yes/no question • a request • Attachment • The cop saw the man with the binoculars.

7. Local and Global Ambiguities • Local ambiguities • An ambiguity that arises at some local level, but it is resolved at the global level • Global ambiguities • The entire sentence can be analyzed in more than one way • resolution of global ambiguities • context • domain knowledge • statistical information

8. Pronoun Comprehension • Pronouns are one type of ambiguity Clinton confessed to Gore when he asked for the truth. • Different factors affecting pronoun comprehension • gender • number • person • order of mention • center of attention

9. Truth Table • A truth table is a conventionalized arrangement of all the possible combinations of truth values for the components of a proposition or argument. • A truth table for statement PQ

10. Boolean Connectives

11. entailment |= • is a set of sentences • is a sentence example: {John is a bachelor} entails John is an unmarried adult male.

12. possible worlds semantics • On the possible worlds theory, propositions are identified with sets of possible worlds. A proposition p is true at a possible world w if and only if w is a member of p. • In the framework of possible world semantics, linguistic expressions are assigned extensions "at" possible worlds. Thus, names, n-place predicates and sentences are assigned individuals, sets of n-tuples of individuals, and truth values, respectively, at different possible worlds. Intuitively, possible worlds are to be thought of as "ways things could have been"

13. First Order Logic • a model: domain = {john, mike, sarah, alice, natalia} i(man)={john,mike} i(woman)={sarah,alice, natalia} i(loves)={(john,sarah),(mike,alice)} • In this model, • Entities are john, mike, sarah, alice, natalia • Predicates are man, woman, and loves

14. First Order Logic (2) Sentence “Every man loves a woman” can then be translated to: • where • x and y are variables • is universal quantifier, meaning “for all” • is existential quantifier, meaning “there exists”